:root {
    --primary-color: #007bff;
    --success-color: #28a745;
    --danger-color: #dc3545;
    --light-gray: #f8f9fa;
    --medium-gray: #e9ecef;
    --dark-gray: #6c757d;
    --border-color: #dee2e6;
}
body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    margin: 0;
    background-color: var(--light-gray);
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}
.header {
    background: #fff;
    padding: 15px 30px;
    font-size: 24px;
    font-weight: 600;
    color: #333;
    border-bottom: 1px solid var(--border-color);
    text-align: center;
    flex-shrink: 0;
}
.main-content {
    display: flex;
    flex-grow: 1;
    overflow: hidden;
}
.sidebar {
    width: 450px; /* Tăng chiều rộng sidebar một chút */
    background: #fff;
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    padding: 20px;
    overflow-y: auto;
    flex-shrink: 0;
}
.preview-area {
    flex-grow: 1;
    padding: 20px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    overflow: hidden;
}
.section {
    margin-bottom: 20px;
}
.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--border-color);
}
.collapsible-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 15px;
}
#collapse-icon {
    transition: transform 0.3s ease;
}
#collapse-icon.collapsed {
    transform: rotate(-90deg);
}
.files-list.hidden {
    display: none;
}
label {
    font-weight: 600;
    color: #495057;
    font-size: 18px;
}
.upload-section {
    border: 2px dashed var(--border-color);
    padding: 20px;
    border-radius: 8px;
    text-align: center;
    background-color: #fafafa;
}
.upload-section p { margin: 5px 0; font-size: 16px; font-weight: 500; }
.preview-wrapper {
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
    background-color: #fff;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 20px;
    box-sizing: border-box;
}
#previewCanvas {
    max-width: 100%;
    max-height: 100%;
    cursor: grab;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}
#downloadBtn {
    background-color: var(--success-color);
    color: white;
    padding: 15px 25px;
    border: none;
    border-radius: 8px;
    font-size: 18px;
    font-weight: 500;
    cursor: pointer;
    width: 100%;
    margin-top: auto; /* Đẩy nút xuống dưới cùng */
    transition: background-color 0.2s;
}
#downloadBtn:hover { background-color: #218838; }
#downloadBtn:disabled {
    background-color: var(--medium-gray);
    color: var(--dark-gray);
    cursor: not-allowed;
}
.files-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}
.file-item {
    padding: 10px;
    background-color: var(--light-gray);
    border-left: 3px solid var(--primary-color);
    border-radius: 4px;
    font-size: 14px;
    font-weight: 500;
}
.file-item.error {
    border-left-color: var(--danger-color);
    color: var(--danger-color);
}
/* AI Section Styles */
.ai-section {
    display: flex;
    flex-direction: column;
    gap: 10px;
}
.ai-textarea {
    width: 100%;
    min-height: 60px;
    padding: 10px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    resize: vertical;
    box-sizing: border-box;
    font-size: 14px;
}
#ai-input {
    min-height: 40px;
}
#ai-tags-output {
    min-height: 80px;
}
#generateAiBtn {
    background-color: var(--primary-color);
    color: white;
    padding: 12px;
    border-radius: 8px;
    border: none;
    font-size: 16px;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.2s;
}
#generateAiBtn:hover {
    background-color: #0056b3;
}
#generateAiBtn:disabled {
    background-color: var(--medium-gray);
    cursor: wait;
}